Studies aimed to improve the mechanical properties, thermal properties, electrical properties, and the like of metal material by dispersing a heterogeneous carbon nano material, such as carbon nanotubes or fullerene (e.g. C60), therein have been actively carried out for the last 10 years. In the early stages after the manufacture, most carbon nano materials are present in the form of being coagulated by van der Waals force due to their small size. It is therefore very difficult to disperse such nano materials in a material, such as a metal, which has a very compact crystal structure, by dividing respective particles of the nano material. Therefore, studies on composites using such carbon nano materials are not active.
Taking fullerene as an example, most overseas research achievements reported to date used a powder process (E. V. Barrera, J. Sims, and D. L. Callahan, J. Mater. Res. 1995; 10; 367) or a casting process (F. A. Khalid, O. Beffort, U. E. Klotz, B. A. Keller, P. Gasser, S. Vaucher, Acta Mater. 2003; 51; 4575). Recently, a research achievement using steel plastic deformation (T. Tokunaga, K. Kaneko, K. Sato, Z. Horita, Scripta Mater. 2008; 58; 735) was published. However, the metal/fullerene composite produced through the foregoing research result does not exhibit any merits as nano particles, since the size of the fullerene particles is on the order of tens of micrometers.
Although one fullerene molecule is a very fine particle having a size of about 1 nm, fullerene particles are bonded together such that they form a face-centered cubic (fcc) structure, and are present in the form of powder having a size on the order of tens of micrometers in the early stage. In the above research, since fullerene particles having the shape of the early stage are dispersed in the metal matrix, fullerene is present as particles having a size of tens of micrometers instead of being dispersed as nano particles. In addition, when the powder process is used, fullerene particles having a size on the order of tens of micrometers are present on the surface instead of penetrating into the metal powder. Since such particles obstruct intermolecular bonding when integrated, it is difficult to manufacture a bulk material and commercial applicability is lacking. The use of the casting process makes the manufacturing process easier and simpler than the case of using the powder process, thereby achieving excellent commercial applicability. However, in casting, fullerene rises to the surface of molten metal and does not mix with metal, because the specific gravity of fullerene is lower than that of metal. Therefore, because of the foregoing difficulties in the manufacturing process, there are no precedents to date in which a metal-carbon nano material composite that has realized advantages and excellent characteristics of a nano-size carbon material, such as fullerene or carbon nano tubes, has been developed to the present.